This invention relates generally to gas generation and, more particularly, to gas generation via alkali metal perchlorate-containing gas generant compositions which produce or result in gaseous effluents having reduced levels of various undesirable constituent.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag cushion” that is inflated or expanded with a gas when a vehicle experiences a sudden deceleration, such as in the event of a collision. Such airbag restraint systems normally include: one or more airbag cushions, housed in an uninflated and folded condition to minimize space requirements; one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden deceleration of the vehicle; an activation system electronically triggered by the crash sensors; and an inflator device that produces or supplies a gas to inflate the airbag cushion. In the event of a sudden deceleration of the vehicle, the crash sensors trigger the activation system which in turn triggers the inflator device which begins to inflate the airbag cushion, typically, in a matter of milliseconds.
Many types of inflator devices have been disclosed in the art for inflating one or more inflatable restraint system airbag cushions. Inflator devices which form or produce inflation gas via the combustion of a gas generating pyrotechnic material, e.g., a “gas generant,” are well known. For example, inflator devices that use the high temperature combustion products, including additional gas products, generated by the burning of the gas generant to supplement stored and pressurized gas to inflate one or more airbag cushions are known. In other known inflator devices, the combustion products generated by burning the gas generant may be the sole or substantially sole source for the inflation gas used to inflate the airbag cushion. Typically, such inflator devices include a filter to remove dust or particulate matter formed during the combustion of a gas generant composition from the inflation gas to limit or prevent occupant exposure to undesirable and/or toxic combustion byproducts.
In view of an increased focus on passenger safety and injury prevention, many automotive vehicles typically include several inflatable restraint systems, each including one or more inflator devices. For example, a vehicle may include a driver airbag, a passenger airbag, one or more seat belt pretensioners, one or more knee bolsters, and/or one or more inflatable belts, each with an associated inflator device, to protect the driver and passengers from frontal crashes. The vehicle may also include one or more head/thorax cushions, thorax cushions, and/or curtains, each with at least one associated inflator device, to protect the driver and passengers from side impact crashes. Generally, the gaseous effluent or inflation gas produced by all of the inflator devices within a particular vehicle, when taken as whole, are required to satisfy strict content limitations in order to meet current industry safety guidelines. Thus, it is desired that the gas generant compositions used in such inflator devices produce as little as possible of undesirable effluents such as hydrogen chloride, carbon monoxide, ammonia, nitrogen dioxide and nitric oxide.
There is a need and a demand for gas generant compositions which produce or result in desirably low levels of undesirable effluents such as hydrogen chloride, carbon monoxide, ammonia, nitrogen dioxide and nitric oxide. While the manipulation of the equivalence ratio of gas generant materials is a technique commonly used to adjust the effluent levels of gas generant materials, such manipulation is prone to performance sometimes referred to as the equivalence ratio “teeter-totter”. That is, as the equivalence ratio is lowered, under-oxidized species, such as CO and NH3, increase and over-oxidized species, such as NO and NO2, decrease. The reverse is true when the equivalence ratio is increased.
In view of the above, there is a need and a demand for pyrotechnic gas generant compositions that, when employed in an airbag inflator device, produce a gas effluent that is substantially free of undesired gaseous effluents such as carbon monoxide, ammonia, nitrogen dioxide and nitric oxide.